You can find both files above in
+ Open templates/ja_bookshop/css/error.css file
Line 17:
@import url(http://fonts.googleapis.com/css?family=Roboto:400,100,700);
+ Open templates/ja_bookshop/css/offline.css file
Line 6, 7:
@import url(http://fonts.googleapis.com/css?family=Roboto:400,300,700);
@import url(http://fonts.googleapis.com/css?family=Roboto+Slab:400,300,700);
+ Open templates/ja_bookshop/tpls/blocks/head.php file
Line 53, 54:
<link href='http://fonts.googleapis.com/css?family=Roboto:400,700,300' rel='stylesheet' type='text/css'>
<link href='http://fonts.googleapis.com/css?family=Roboto+Slab:400,300,700' rel='stylesheet' type='text/css'>